Display screens are used in a wide variety of applications, such as home and commercial large screen televisions, laptop and desktop computers, and indoor and outdoor advertising and information presentations. So-called flat panel displays are only a few inches thick in contrast to deep cathode ray tube monitors found on most televisions and desktop computers. Flat panel displays are a necessity for laptop computers, but also provide advantages in size and weight for many other applications. Currently, laptop computer flat panel displays utilize liquid crystals which can be switched from a transparent state to an opaque state by the application of small electrical signals. It is difficult to reliably produce these displays in sizes larger than those suitable for laptop computers.
Plasma displays have been proposed as an alternative to liquid crystal displays. Plasma displays utilize tiny pixel cells of electrically-charged gases to produce an image and require relatively large electrical power to operate.
Display panels having a cathode using a field emission electron source, i.e., a field emission material or field emitter, and a phosphor capable of emitting light upon bombardment by electrons emitted by the field emitter have been proposed. Such display panels have the potential for providing the visual display advantages of conventional cathode ray tubes and the depth, weight and power consumption advantages of flat panel displays. U.S. Pat. Nos. 4,857,799 and 5,015,912 disclose matrix-addressed flat panel displays using micro-tip cathodes constructed of tungsten, molybdenum or silicon. WO 94-15352, WO 94-15350 and WO 94-28571 disclose flat panel displays wherein the cathodes have relatively flat emission surfaces.
It has now been discovered that a fibrous cathode provides advantages over a cathode having a relatively flat emission surface. The fibrous cathode is supported by a substrate and further improved performance is achieved when the portions of the fibrous cathode addressed, and from which electron emission occurs, are suspended and not in direct physical contact with the substrate. As a result, there is a need for alternative technology for producing high quality and efficient display panels for all these applications and for producing them in large sizes when required. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the attached drawings and to the detailed description of the invention which hereinafter follows.